The document DE 10 2010 056 457 A1 discloses a windfarm with a plurality of wind turbines. A central control device can calculate target values for the reactive powers that are to be provided by the individual wind turbines. In the event of a network fault of the supply network, these centrally calculated target values are ignored by the individual wind turbines.
Multi-generator power plant arrangements (multi-generator power plants, MGPP) comprise a number of generators for generating electrical power. It is also possible in particular for generators of different types to be combined. For example, a multi-generator power plant arrangement may comprise wind turbines, photovoltaic arrays with individual inverters, electrical storage systems such as for example batteries, flywheels or supercapacitors with individual inverters, diesel generators, gas turbines and/or further generators. All of the generators of such a multi-generator power plant arrangement are brought together at a common point, which is formed as the electrical interface of the multi-generator power plant arrangement with an electrical energy supply network. This electrical interface is referred to as the point of common coupling (PCC). The energy supply network into which the multi-generator power plant arrangement feeds the electrical power may be for example a transmission grid or a distribution grid or else an isolated grid.
In the case of power plant arrangements, a distinction is generally drawn between so-called grid-forming power plants and so-called grid-supporting power plants.
Grid-forming power plants provide the electrical voltage at a specified amplitude and frequency. Examples of grid-forming power plants in the European synchronous grid are nuclear or coal power plants. Grid-supporting power plants feed active power and reactive power into an energy supply network in dependence on the frequency and amplitude of the voltage at the point of common coupling. In the case of grid-supporting power plants, the reactive power is typically adapted in dependence on the amplitude of the voltage at the point of common coupling, even relatively small fluctuations in the amplitude of the grid voltage potentially leading to a significant variation in the reactive power that is fed in. An example of such grid-supporting power plants are windfarms. Such control of the feeding in of the reactive power in dependence on the voltage amplitude is not directly possible in the case of grid-forming power plants because of the voltage amplitude being specified at the point of common coupling. Rather, in the case of grid-forming power plant arrangements, the reactive power that is fed in at the point of common coupling depends on the configuration of the grid and the further generators and loads in the grid.
In the case of multi-generator power plant arrangements, the reactive power to be provided at the network feeding-in point can and must additionally be distributed among the plurality of generators of this power plant arrangement. However, this entails the risk that on the one hand the reactive power to be provided is distributed very unevenly among the generators and that on the other hand reactive currents flow within the multi-generator power plant arrangement, and though not contributing to the reactive power at the point of common coupling do place a great load on the individual generators, and can possibly lead to an overloading of these generators.